fig1

Figure 1. (A) Assembled ceramic tube device; (B) Gas sensing measurement circuit; (C) Structural schematic of the bypass-heated mZnO-based ceramic tube sensing device. Figure A-C is quoted with permission from Zhou et al.^[25]; (D) Schematic diagram of MEMS sensor and its spatial structure; SEM image of the central region of the MEMS chip. Figure 1D is quoted with permission from Yan et al.^[26]. mZnO: Mesoporous zinc oxide; MEMS: microelectromechanical system; SEM: scanning electron microscope.